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961.
Inexpensive synthesis of diamine, 1,4-bis(4-nitrophenoxy)-2-(6-oxido-6H-dibenz <c,e> <1,2> oxaphosphorin-6-yl) phenylene was revealed in this work. Based on the diamine, a series of organosoluble polyamides were prepared by direct polycondensation of the diamine with various aromatic diacids using triphenyl phosphite and pyridine as condensing agents. The number-average molecular weights of the resulting polyamides range from 4.2 × 104 to 10.5 × 104 g/mol, and the weight-average molecular weights are in the range of 7.5-28.2 × 104 g/mol. The Tgs of these polyamides range from 210 to 255 °C by dynamic mechanical analysis. The resulting polyamides are tough and flexible with tensile strength, elongation at break and moduli range from 84 to 101 MPa, 4.8-7.0%, and 2.36-3.22 GPa, respectively. The degradation temperatures (Td 5%) and char yields at 800 °C in nitrogen range from 460 to 486 °C and 59-68 wt%, respectively. The cutoff wavelength of these polyamides falls in the range of 345-366 nm, showing a very light color characteristic. In addition, these polyamides display good oxygen plasma resistance. 相似文献
962.
This paper proposes the most feasible solution to overcome the failure of the 2nd harmonic filter in the static VAR compensator (SVC) which operates with the DC electric arc furnace (EAF) at Gwangyang Steel Mill in Korea. In order to investigate the causes of this failure, various measurements were carried out on the DC EAF and the main transformer at the PCC (point of common connection). It was concluded that the two causes for the failure are; the inrush current in the main transformer, and the parallel resonance between the system impedance and the harmonic filter. Three solutions to suppress the transformer inrush current and another three solutions to avoid the parallel resonance are suggested. The feasibility of these solutions was verified through the computer simulation with PSCAD/EMTDC. The most feasible solution to avoid further failures of the 2nd harmonic filter was selected, based on the estimated result for the six optional solutions in the point of performance and cost. 相似文献
963.
Mechanical properties and durability of PMMA impregnated mortar 总被引:1,自引:0,他引:1
Priya Nair Du Hyun Ku Chul Woo Lee Jung Soon Park Hun Young Park Won Mook Lee 《Korean Journal of Chemical Engineering》2010,27(1):334-339
Polymer impregnated concrete (PIC) is known to exhibit better strength and durability characteristics than the other classes
of polymer cement composites. In the work described herein the monomer was impregnated into cement mortar and polymerized
by two methods — the conventional thermal method and using microwaves. The mechanical properties and durability characteristics
of the samples and on exposure to chemical environments were then evaluated. The above studies revealed that the strengths
of PIC specimens were almost 2–3 times better than those of conventional cement mortars. The chemical resistance was also
found to be superior even on prolonged exposure to the chemical media. This may be attributed to the protective layer formed
by the polymer on the cement mortar, which prevents the external chemical media from interacting with the cement particles.
The properties of the PIC specimens prepared by both methods have also been compared and discussed in this paper. 相似文献
964.
Jae-Young Lee Jiyong Joo Jae Kwang Lee Sunghyun Uhm Eon Soo Lee Jae Hyuk Jang Nam-Ki Kim Yong-Chul Lee Jaeyoung Lee 《Korean Journal of Chemical Engineering》2010,27(3):843-847
We first investigated the effect of partial pressure of hydrogen (H2) on the performance of polymer electrolyte fuel cells (PEFCs) by controlling the ratio of hydrogen and nitrogen (N2). The cell performance with Pt/C anode was significantly decreased with reduction of the partial pressure of H2 in the presence of carbon monoxide (CO), while the performance variation was negligible in the absence of CO. Severe CO poisoning
on Pt/C electrode at low partial pressure of H2 might be attributed to the hindering effect by N2 and CO. On the other hand, PtRu/C anode showed consistent power performance even at low partial pressure of H2. 相似文献
965.
Asemi-empirical atomic potential, the second nearest-neighbor MEAM, has been applied to obtain an atomic potential for the Fe-Cr system, based on the previously developed potentials for pure Fe and Cr. The procedure for the determination of potential parameter values and the performance of the assessed alloy potential were also presented. It was shown that the potential describes the basic thermodynamic property and alloy behavior in the bcc solid solution successfully, as well as many physical properties of pure Fe and Cr. The limit in the applicability of the present potential is also discussed. 相似文献
966.
Kyu-Sung Kim Hyun Seok Lee Young-Min Jeon Joon-Woo Kim Chil-Won Lee Myoung-Seon Gong 《Dyes and Pigments》2009,81(3):174-179
A novel, spiro-type host material 2-(10-naphthylanthracene)-spiro[fluorene-7,9′-benzofluorene] was prepared by reacting 2-bromo-spiro[fluorene-7,9′-benzofluorene] with 9-(2-naphthylanthracene)-10-boronic acid via the Suzuki reaction. 2-4′-(Phenyl-4-vinylbenzeneamine)phenyl-spiro[fluorene-7,9′-benzofluorene], 4-[2-naphthyl-4′(phenyl-4-vinylbenzeneamine)]phenyl and diphenyl-[4-(2-[1,1;4,1]terphenyl-4-yl-vinyl)-phenyl]-amine were used as dopant materials. Devices with the configuration of ITO/N,N′-bis[4-(di-m-tolylamino)phenyl]-N,N′-diphenylbiphenyl-4,4′-diamine)/bis[N-(1-naphthyl)-N-phenyl]benzidine/2-(10-naphthylanthracene)-spiro[fluorene-7,9-benzofluorene]:5% dopant/aluminum tris(8-hydroxyquinoline)/Al-LiF showed a maximum power efficiency of 3.7 cd/A at 17.93 mA/cm2 and a maximum luminance of 5018 cd/m2 at 10 V with a turn-on voltage of 4.5 V. 相似文献
967.
Ju Young Lee Hong Seung Kim Chung-Hyun Lee Hyung Koun Cho Bo Hyun Kong 《Thin solid films》2009,517(17):5157-1130
We report the effects of thermal annealing in air and N2 ambient on the structural, optical, and electrical properties of zinc oxide (ZnO) films deposited on a p-GaN substrate. Also, we report on the fabrication and device characterization of heterojunction light-emitting diodes based on the n-ZnO/p-GaN systems. In the case of N2 ambient, room-temperature electroluminescence (EL) in the violet region with peak wavelength 400 nm was observed under forward bias. In air ambient, EL spectrum consisted of a broad band from 400 nm to 700 nm due to the Ga-O mixed region formed interface between the ZnO and GaN layer. 相似文献
968.
Korea is experiencing an extraordinarily rapid demographic transition. We investigated the short-term association between air pollution and mortality and assessed the impact of improved air quality on mortality in a rapidly aging city, Seoul, Korea.The generalized additive model (GAM) was used to estimate the relative risks (RR) of mortality associated with changes in air pollution. The time trends, seasonal variations, day of the week effects, and weather effects were controlled in the models. To estimate the health benefits, we used the US Environmental Protection Agency's BenMAP.For people 0–64 years of age, elderly people (65+ years), and all age groups, an increase of 10 μg/m3 in PM10 was associated with increases in daily death counts of 0.27% (95% CI: 0.04–0.50), 0.45% (95% CI: 0.27–0.64), and 0.37% (95% CI: 0.23–0.52), respectively. For ages 0–64 years, elderly people, and all age groups, a 10 ppb increase in 1-hour maximum ozone concentration resulted in an increased risk of daily death counts of 0.28% (95% CI: − 0.19–0.74), 0.96% (95% CI: 0.46–1.47), and 0.81% (95% CI: 0.35–1.26), respectively.For elderly people, it was estimated that the health benefits of attaining the World Health Organization's (WHO) air quality guidelines (AQGs) for PM10 (24-hour average 50 μg/m3) would suggest an annual reduction of 964 (95% CI: 564–1366) premature deaths, and 329 (95% CI: 159–500) premature deaths could be prevented annually in 2015 from attaining the WHO's guidelines for ozone (8-hour average 100 μg/m3).The rapid increase of the elderly population has major consequences and implications for society and public health. This study showed that elderly people are at higher risk for the acute mortality effects of air pollution. Therefore, cleaner air will substantially contribute to improved public health in Seoul, given the growing concern about the adverse effects of air pollution for elderly people. 相似文献
969.
Based on the investigation of the characteristics of construction sites in terms of AR technology suitability, this paper introduces the application of a new framework of ubiquitous augmented reality (AR) technology (titled U-AR) to a construction site where high mobility, free from occlusion, good accuracy, and expandability into large scale applications play a key role in meeting the practical requirements. U-AR is intended to enhance accessibility to the distributed networks that provide a gateway between a physical construction site and the digital information of AR. To illustrate the U-AR system, the detailed schematic architecture of the AR display technique, motion tracking method, and server implementation is discussed throughout the preliminary studies. The proposed architectures of U-AR present a direction of what technologies regarding display, tracker, and server should be focused for the development of the compelling U-AR. It is found that the proposed U-AR is expected to be the best suitable technology to provide AR-based visual information in construction sites. 相似文献
970.
Kyung-Woon Jang Kyung-Wook Paik 《Electronics Packaging Manufacturing, IEEE Transactions on》2009,32(2):74-80
In this paper, the effects of anisotropic conductive film (ACF) viscosity on ACF fillet formation and, ultimately, on the pressure cooker test (PCT) reliability of ACF flip chip assemblies were investigated. The ACF viscosity was controlled by varying the molecular weight of the epoxy materials. It was found that the ACF viscosity increased as the increase of molecular weight of the epoxy materials. However, there was little variation of the thermomechanical properties among the evaluated ACFs with different viscosites. Also, the results showed that the ACFs have no differences in moisture absorption rate, die adhesion strength, and degree-of-cure. In scanning electron microscopy images, the lower ACF viscosity resulted in the smoother ACF fillet shape and the higher fillet height. From the results of PCT, the ACF flip chip assembly with the smoother fillet shape showed better reliability in terms of contact resistance changes. After 130 h of PCT, the flip chip assembly with lower ACF viscosity also showed a lesser degree of delamination at the ACF/chip interface. 相似文献